This invention relates to the construction industry and more particularly to those substantially elastomeric devices intended to make apertures of predetermined configuration in such plastic materials as cement or the like. In further particularity, such apertures are of relatively small dimensions as conduit openings through walls, floors, or shallow receptacles therein.
In the erection of buildings or other structures made of cement, or a similar hardenable plastic material, it is frequently necessary to provide holes in the floor slabs. These holes are intended to accommodate or receive water or steam pipes, electrical conduits, and the like. The passage of steam pipes from a basement-installed boiler upwardly to the various rooms is but one example of the need for pre-formed floor openings. The passage of electrical conduits or water pipes, not only from floor to floor but between rooms, is but another example of the need for pre-formed holes. In addition, because of the varying sizes of such conduits, pipes, and the like, the shape of the holes need not necessarily by cylindrical. Thus, while cylindrical openings may be preferable, such opening may also be elipsoid, semi-cylindrical, and so on.
In the past, a number of devices have been suggested for forming openings in such hardenable plastic material as cement. Some devices have been intended to form conduits of substantial length, as in cement pipes or channels running the length of walls. Most frequently, devices for such conduits include the use of a thin-walled rubber tube having wires or cables drawn therethrough so that when the plastic material hardens, the wires may be pulled upon to deform the rubber tube away therefrom, thereby forming the conduits. Their construction, however, is exceedingly complicated and not readily applicable to such uses as forming of smaller apertures through cement walls and floors.
Amongst the aperture forming devices for forming pipes that have been suggested is one proposed by Murray (U.S. Pat. No. 1,534,134). Murray proposes the use of a highly resilient solid rubber member to be placed in a mold box. This particular means of forming a pipe in a hardenable plastic material, such as cement, is most difficult to be used since there is no ready means of removal of the rubber when the cement has hardened. As disclosed by Murray, however, the solid rubber member is disposed adjacent a mold box cover. It is believed that as such, the rubber unit may be easily plied out of the box, leaving a channel therein. If one were to attempt to draw the rubber solid along its length then the forces at the very edge of the resilient solid, it will cause the rubber solid to break apart and remain within the cement itself.
A number of expedients are believed to have been resorted to in the creation of floor and wall slab holes of smaller dimension. One common practice is to nail an inverted previously opened beer or soft drink can directly to the floor or wall foundation prior to pouring the concrete. After the concrete has been poured, the circular wall at the top of the can may be punctured and an effort can be made to pull the can from its surrounding cement by means of a hook. However, due to the strong bond which frequently obtains between the metal can and the surrounding concrete, it becomes difficult to extract the can. Simetimes the can is merely left within the wall. However, can sizes are of limited dimensions and not readily available for the numbers of holes required. Further, the existence of ragged metal edges at an opening is not desirable. Cutting tools required to cleanly cut open such cans for more established use on a construction site would be an added inconvenience and cost, as well as the cost of material. It should be borne in mind that for everyone of the many, many holes in such construction, cans would be required which could not be reused.
Another approach to making apertures in a plastic type material is that suggested by Bowden et al. (U.S. Pat. No. 3,469,817). Bowden et al. suggests a hole pattern member formed of an elastomeric material. The member comprises a cylindrical casing with spokes or veins terminating substantially at the center thereof, the hub or center of the member is twisted, the veins thereby draw in the outer cylindrical surface so as to expedite removal from the concrete. The difficulty with this device is that in frequent usage, the veins must be constantly flexed, thereby resulting in what is believed a limited life span. What is more, cement may eventually find its way between the veins, thereby restricting the ability of the user to collapse the member so that it may be removed from the cement structure.
The longer the length, more than five inches, the veins will, it is believed, fail to fully collapse. In addition, cement walls may, by virtue of the weight of the cement, cause the device to prematurely flex, thereby rendering the aperture useless. What is more, the forces necessary to deform the casing are applied directly and radially through the spokes, thereby requiring a direct deal of force. The frequent flexing and the considerable internal deformation makes this device, it is believed, to be inconvenient and of a limited reuse life.
In the making of apertures in plastic materials, Chetirko (U.S. Pat. No. 3,172,163) has suggested one approach, but one not suitable to hardenable plastic materials. In this instance, Chetirko recommends the use of a rigid core for reducing the hole size in bowling balls. The core is threaded and a bolt is pushed down through it so that after the material is hardened, the bolt may be pushed down and cut the base, thereby removing the core from the bowling ball. However, if this were done with an elastomeric material, the result would be that it would deform under the pressure and the bolt would be removed, leaving the elastomeric material securely within the cement structure.